mev-toolkit/notes/ethereum.md

Ethereum notes

Basics

• the existence of a Turing-complete programming language means that arbitrary contracts can be created for any transaction type or application.

• a state is made up of objects called "accounts", with each account hacing a 20-byte address and state transitions being direct transfers of value and information between accounts.

• an Ethereum account contains four fields:

  • the nounce: a coutner used to make sure each transaction can only be processed once
  • the account's current ether balance
  • the account's contract code
  • the account's storage

• there are two type of accounts: externally owned accounts (controlled by private keys) and contract accounts (controlled by their contract code)

• a transaction refers to the signed data package that stores a message to be sent from an externally owned account. It contains:

  • the recipient of the message
  • a signature identifying the sender
  • the amount of ether to transfer from the sender to the recipient
  • an optional data field
  • STARTGAS, representing the maxium numner of computation steps the transaction is allowed to take
  • GASPRICE, representing the fee the sender pays per computation step

• contracts can send "messages" to other contracts, which are virtual objects that are never serialized and exist only in the Ethereum execution environment. It contains:

  • the sender of the message (implicit)
  • the recipient of the message
  • the amount of ether tot transfer alongside the message
  • an optional data field
  • STARTGAS

• a message is like a transaction, except it is produced by a contract and not an external actor. A message is produced when a cotnract currently executing code executes the CALL opcode.

Code execution

• the code in Ethereum contracts is written in a low-level, stack-based bytecode language, referred as the EVM.

• The operations have access to three types of space in which to store data:

  • the stack, a last-in-first-out container to which values can be pushed and popped
  • memory, an infinite expandable byte array
  • contract's long-term storage, a key/value store (persist long term)